Typically electronic devices are cooled by means of passive natural radiation from an associated heat sink device, usually constructed of aluminum. High powered electronic devices, however, generate large amounts of heat and require specialized cooling systems to prevent overheating.
A simple system once commonly used to cool airborne electronics in the 1950's and 1960's was a ducted air apparatus wherein air flowing past the exterior of an aircraft was directed past the electronic devices to air cool them directly. This method of cooling has been abandoned for several reasons. One important defect with this method was that contaminants carried in the cooling air were deposited on the electronic components and circuitry. These deposits caused component damage and failure in addition to decreasing cooling efficiency. Secondly, this type of simple air duct system is incapable of adequately cooling modern electronic components since electronic components have changed radically in the last decade and have become smaller and more powerful. Small powerful components produce large amounts of heat in a smaller area and thus result in a large cooling load. Passing a sufficient quantity of cool air past such components raises difficult problems. Further, as aircraft speeds have increased and component size has decreased, directly subjecting such components to a possibly damaging airstream has become impracticable. For these reasons more complex cooling systems have been devised which cool components indirectly by conduction.
An element common to most modern airborne electronics conductive cooling systems is a cold plate which conducts heat away from electronic modules. Cold plate systems generally introduce a heat loss penalty of 30.degree.-40.degree. C. between the coolant and electronic devices to be cooled. This heat penalty increases the heat load on the coolant and increases the amounts of coolant required to properly cool the electronic devices. Common coolants used in evaporative cooling systems include water and freon. An example of a modern cooling system is found in U.S. Pat. No. 3,776,305 to Simmons. Simmons utilizes a mixture of different systems and coolants. Such systems tend to require a relatively high level of complexity and as a result are somewhat unreliable.
A common type of conductive cooling system utilizes freon refrigerant to cool heat transfer cold plates adjacent to the electronic devices. This relatively complex system is similar to that used in a conventional refrigerator and requires relatively long conductive paths with their associated heat losses. An energy cost is also incurred in driving the freon through the cooling system.
It is therefore an object of this invention to provide a direct air cooling system that is relatively uncomplicated yet solves the problems previously associated with direct air cooling systems.
In view of the above objective a need arises for providing large quantities of air for the direct air cooling system. Conventional external air scoops are capable of providing large quantities of ram air, however, aircraft drag and aesthetics dictate against the use of external air scoops. This is especially true in modern aircraft where pod and aircraft fuselage streamlining is carried to the extreme in order to lower aircraft drag and improve aircraft manuverability. As a result the submerged type of air scoop is greatly preferred. Unfortunately, it is well know that submerged air scoops are subject to choking and are inferior collectors of air as compared to the older external air scoops which are placed away from the aircraft fuselage or pod. An object of this invention is therefore to provide a submerged air scoop capable of providing large quantities of air to a direct air cooling system.
As stated above; previous direct air cooling systems have had major problems due to air flow contamination. A further object of this invention therefore, is to limit air flow contamination and avoid exposure of electronic devices to contaminants without compromising the cooling of the electronic components.